# Cos2θ to sinθ? Identity conversions

• Nov 28th 2012, 06:56 PM
whittwhitt
Cos2θ to sinθ? Identity conversions
How to find cos2θ if sinθ = 2?

How to find cosθ if sin2θ = 3?

Both lie in quadrant I. I'm unsure how to convert from one identity to the other ...
• Nov 28th 2012, 07:03 PM
jakncoke
Re: Cos2θ to sinθ? Identity conversions
How can $sin(\theta) = 2$ if its maximum value is 1.
• Nov 29th 2012, 03:15 AM
skeeter
Re: Cos2θ to sinθ? Identity conversions
In this post ...

http://mathhelpforum.com/trigonometr...equations.html

...you were requested to post specific problems rather than cryptic references to double angle problems. Now it seems you're making up stuff, because you really don't know what you're doing.

Post a specific problem from a text or as given by your instructor.
• Nov 29th 2012, 05:42 AM
topsquark
Re: Cos2θ to sinθ? Identity conversions
Quote:

Originally Posted by whittwhitt
How to find cos2θ if sinθ = 2?

How to find cosθ if sin2θ = 3?

Yes. Impossible. $-1 \leq sin(\theta) \leq 1$. For any angle in any quadrant.